The present invention generally relates to a technical field of wiring films to be used in minute semiconductor devices; and more particularly, the present invention relates to a technical field of electrode layers and wiring layers to be in contact with glass substrates.
In recently manufactured electric products (such as, FPDs (Flat panel display), thin-film solar cells or the like), transistors are required to be uniformly arranged on a wide substrate, so that amorphous silicon (including hydrogenated amorphous silicon) or the like, which can form semiconductor layer having uniform characteristics on the substrate with large area, are used.
Amorphous silicon can be formed at a low temperature and causes no adverse affect on other materials, but it has a defect in that the mobility is low. Consequently, oxide semiconductors, which can form thin films having high mobility on a large area substrate at low temperatures, have been attracting attention.
Further, in addition to the oxide semiconductors having the high mobility, displaying with uniform brightness has recently been tried by using copper thin films having low resistances in electrode layers and wiring layers of transistors of semiconductor integrated circuits and the FPDs.
However, the copper thin film has poor adhesion to the glass substrate, the oxide semiconductor and the oxide thin film, and copper atoms as a constituting material of the copper thin film diffuse into the semiconductor or the oxide thin film, which may cause reduction in reliability.
More particularly, when a wiring layer and a gate electrode layer are formed on a glass substrate, it is feared that the wiring layer and the gate electrode layer may be peeled, because the copper thin film has poor adhesion to the glass.
In this case, although an adhering film (such as, a TiN film, a W film or the like), which increases adhesion strength of the copper wiring to the glass substrate has been provided between the copper thin film and the glass substrate, there is a problem in that the cost increases. These problems are disclosed in JPA2008-203808 and JPA 2008-311283, for example.
Furthermore, the copper thin film is difficult to be dry etched, and is generally formed by a wet etching method. However, because the copper thin film and the adhering film (such as, the TiN film, the W film or the like) cannot be etched with the same etching liquid, a laminated film having a two-layer structure of the copper thin film and the adhering film cannot be etched in a single etching step.
For this reason, an adhering film having adhesion and being able to be etched with the same etching liquid as for the copper thin film has been sought.